I Hope We are lucky enough to just see a beautiful and unique show in the sky but I believe there is the chance we have, at least, a few more crashes
like the one that hit Chelyabinsk in Russia, by December.

I`m far from being an expert on this subject, but I believe NASA can`t predict a lot of possible situations that may happen such as magnetic
interferences and/or crashes with other asteroids in space that can change ISON trajectory and if this happens near Earth we can all be surprised
without even a warning.

So, I don`t believe NASA is Lying or Hiding something. Maybe They know there are 99% chances of nothing serious happen but there still is a 1% chance
of surprises coming from the fireball shower that might happen.

Here are some videos I find interesting:

What do you believe will happen ? ....Just a bright comet in the sky or a massive fireball shower that may (or not) hit Earth in unpredictable places
?

I`m far from being an expert on this subject, but I believe NASA can`t predict a lot of possible situations that may happen such as magnetic
interferences and/or crashes with other asteroids in space that can change ISON trajectory and if this happens near Earth we can all be surprised
without even a warning.

What "magnetic interferences?" While there is a very, very, very, very remote possibility that another object might
collide with a comet the chance that such an event would change the orbit such that it would impact Earth is even more remote. And C/2012 S1 (ISON)
will never be near Earth in the first place.

Fireballs are not necessarily the result of large objects. In fact most of them are quite small.
Comet tails are composed of small and "fluffy" meteoroids. They burn up before reaching the surface.

Based upon photographic fireball studies, cometary meteoroids have extremely low densities, about 0.8 grams/cc for class IIIA fireballs, and 0.3
grams/cc for class IIIB fireballs. This composition is very fragile and vaporizes so readily when entering the atmosphere, that it is called
“friable” material. These meteoroids have virtually no chance of making it to the ground unless an extremely large piece of the comet enters the
atmosphere, in which case it would very likely explode at some point in its flight, due to mechanical and thermal stresses.

If we do pass through the dust tail of the comet it won't be until January. At that time we will pass through the area where the comet will have been
in early November. Where it will have left its trail of dust.

It's not certain that we will pass through the dust tail of the comet though, it will still be above the plane of the ecliptic when it passes Earth's
orbit. It could give us a nice show but since the comet doesn't seem to be living up to early hopes...we'll just have to wait and see.

Can anybody (Phage, perhaps?) explain to me, as well as anyone else out there wondering, how the comet could be losing 100,000lbs of dust every minute
if the dust is supposedly weightless in space? Is this a calculated value using our know gravity and some sort of accurate measure of mass from the
comet droppings or is this a guestimate?

How do they know how large in lbs/tons/Kg etc. this thing really is? I'm just skeptical of all the weights of objects in space that I hear thrown
around these days.

There is a difference between weight and mass but both are expressed in the same units. The comet (and its dust tail) are weightless because they are
in freefall around the Sun, just as the astronauts in the ISS are weightless because they are in freefall around the Earth. But they still have
mass.

Those numbers are estimates based on very little data and observations of past comets.

I just always think it is strange to hear talk of weight in space when we have been told since day one that objects in space are pretty much
weightless. I figured that the scientists must apply some calculations using Earth's gravity to get the estimates but could never figure out why it
matters. Wouldn't it make more sense to speak in terms of volume of mass/density changed or lost?

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Just something I was thinking about, please answer if you have time as it is off-topic somewhat
If two objects in space are moving at significant velocity on intersecting vectors and they collide head-on how do they calculate the energy released
at impact? Is weight a factor or is it a strict mass/density/velocity kind of equation?

Is that similar to what happens with calculating collision energy in the LHC?

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